DIET AND GROWTH OF GREAT CORMORANT (PHALACROCORAX-CARBO) NESTLINGS INA MEDITERRANEAN ESTUARINE ENVIRONMENT (AXIOS DELTA, GREECE)

The diet and growth of great cormorant (Phalacrocorax carbo) nestlings were studied in the Aries Delta, Greece in 1993 and 1994. The diet, b ased on analyses of regurgitations, consisted of fish from 12 families . In both years, the dominant prey were the goby Gobius jozo and mulle ts (Mugilidae). There were changes in number and wet-biomass prey comp osition during the study, probably due to the opportunistic foraging b ehavior of the birds. Most prey occurred in aquatic environments at al l salinity levels, consisted mainly of benthic fish, and had no partic ular economic value. The growth of great cormorant nestlings was analy zed using a modification of the method proposed by Ricklefs and White (1975). Sets of estimated values for all variables studied (tarsus, bi ll, bill + head, and weight) plotted against age yielded sigmoidal cur ves. The increase in all growth variables over time was best described by the logistic equation. Body weight and tarsus increased at similar rates, and were faster than those for the bill and the bill + head me asurements. The inflection point was reached by the tarsus, bill, bill + head, and weight at 10.0, 15.7, 13.5, and 18.6 days, respectively. The potential adaptive significance of this growth pattern is discusse d.